Discovery of new therapeutic compounds for treating diseases has typically involved screening individual compounds against targets representative of a particular disease of interest. The iterative process relies upon finding a compound having at least a minimal level of activity in an assay and then synthesizing as many derivatives of the lead compound as possible. The derivatives tested would form the basis of a "structure-activity relationship" (SAR) which would hopefully provide insight for designing a lead compound. Often the process is repeated time and again before any lead is uncovered. The obvious and major drawback in this drug discovery process is the generation of compounds on a one-at-a-time basis requiring much labor, time and expense.
Advances in robotics and solid-phase chemical synthesis has spawned the combinatorial approach for preparing libraries of compounds which makes synthesizing thousands of diverse compounds feasible. What once took months or even years by the traditional approach has become possible in a matter of weeks and even days through combinatorial chemistry, thereby drastically reducing the time, labor and expense involved in drug discovery.
The combinatorial approach has been adapted for preparing vast libraries of oligomeric compounds such as peptides and non-oligomeric small organic molecules on the order of 10.sup.2 to 10.sup.6 discreet compounds. Theoretically the total number of compounds in a library is limited only by the number of available reagents for forming substituents on a central scaffold.